What is photosensitive glue?
The photosensitive glue on the screen printing screen is a material that plays a key role in the screen printing process. The following is a detailed introduction for you:
Composition
Photosensitive resin: This is the core component of photosensitive glue, which determines the sensitivity of photosensitive glue to light and its curing characteristics. Different types of photosensitive resins are suitable for different printing needs. For example, diazo photosensitive resin is a more commonly used one. It has good sensitivity to ultraviolet light and can cure quickly after exposure.
Gel forming agent: The main function is to make the photosensitive glue have a suitable gelling state, which is convenient for coating on the screen and maintaining a certain viscosity and stability. Common gelling agents such as polyvinyl alcohol (PVA) can cooperate with photosensitive resins to make the photosensitive glue have good coating properties when not exposed, and can form a firm cured layer after exposure.
Additives: including plasticizers, defoamers, preservatives, etc. Plasticizers can increase the flexibility of photosensitive glue after curing, making the screen less likely to break during printing; defoamers are used to eliminate bubbles generated during the coating process to ensure the uniformity of the photosensitive glue layer; preservatives can prevent the photosensitive glue from being eroded by microorganisms and deteriorating during storage and use.
Classification
Classification by photosensitive wavelength:
Ultraviolet photosensitive adhesive: This is the most common type, which is mainly sensitive to ultraviolet light (wavelength range is generally 200-400nm). Since ultraviolet light sources are relatively easy to obtain in screen printing platemaking equipment and the cost is relatively low, ultraviolet photosensitive adhesive is widely used.
Visible light photosensitive adhesive: This type of photosensitive adhesive is sensitive to certain specific wavelengths of light in the visible light range, such as blue light, green light, etc. Although it is relatively rarely used, in some special printing scenarios, such as when specific colors of visible light are required for exposure, visible light photosensitive adhesive will be selected.
Classification by curing state:
Solvent-based photosensitive adhesive: The film layer formed after curing is relatively hard, with high wear resistance and solvent resistance, and is suitable for printing some items that need to withstand greater friction or contact more solvents, such as plastic products, metal products, etc.
Emulsion-type photosensitive adhesive: The film layer after curing is relatively soft and has better flexibility, which is more suitable for printing some materials with higher flexibility requirements, such as textiles, leather, etc.
Performance characteristics
High sensitivity: It can quickly respond to light of a specific wavelength and complete the exposure and curing process in a shorter time, thereby improving the efficiency of plate making.
High resolution: It can form fine patterns and texts to meet some occasions with high requirements for printing precision, such as the printing of electronic component identification, high-end cosmetic packaging, etc.
Good adhesion: It can adhere firmly to the screen and will not fall off easily during the printing process, ensuring the service life and printing quality of the screen.
Good chemical stability: When facing chemical substances such as ink and solvent, it can maintain its own chemical properties unchanged and will not dissolve or deteriorate due to contact with these substances.
Function
Plate making function: Through processes such as exposure and development, a transparent or non-transparent area with a printed pattern is formed on the screen, which provides a plate making basis for screen printing, so that the ink can be accurately transferred to the printing substrate according to the predetermined pattern.
Protect the screen: A protective film is formed on the surface of the screen to prevent the screen from being eroded and damaged by factors such as ink and printing pressure during the printing process, thereby extending the service life of the screen.